This invention relates to the measurement of a gap between two members of a mechanical structure, including a mapping of gap width along an interface between the two structural members, to enable manufacture of a shim for insertion between the two structural members while mating conformably to any undulations which may be present in interfacing surfaces of the gap.
Many forms of mechanical structure are manufactured by forming component parts of the structure followed by an assembly of the parts to produce the structure. During the assembling of the component parts, it may be necessary to introduce a shim between interfacing surfaces of the component parts. In some situations, such as in the construction of an aircraft wing, the interfacing surfaces may extend over several or more inches in each of two orthogonal dimensions. With such a wide area to be covered by the shim, it is to be anticipated that the shim may have to vary in thickness in order to match the configuration of the gap defined by the two interfacing surfaces.
A problem arises, particularly in the construction of the aircraft wing, that the configuration of the gap may vary as the component parts of the structure are being positioned, particularly in the situation wherein a number of persons are involved simultaneously in the positioning of the component parts. This may be caused by flexure or distension of the component parts. The result is a changing configuration of the gap between the interfacing surfaces. It is noted that a gap-measurement apparatus or process must not introduce any stresses in the mechanical structure as by changing the gap dimensions, for example, such as by pressing apart faces of the gap. A further problem arises in that the gap may be in a position which is substantially inaccessible to personnel assembling the component parts. Both of these problems introduce difficulties in the measurement of the gap, and necessitate an iterative process for forming a shim to fit the gap properly.